使用Swift p2/OAuth2的OAuth2访问令牌的并行刷新请求 [英] Parallel refresh requests of OAuth2 access token with Swift p2/OAuth2

问题描述

我正在使用 https://github.com/p2/OAuth2 连接到后端我的应用通过OAuth2运行，效果很好.

I am using https://github.com/p2/OAuth2 for connecting to the backend of my app via OAuth2 which works quite well.

我遇到的问题是，当访问令牌过期并且多个请求同时发生时，其中一些失败.

The problem I have is when the access token expires and multiple requests happen at the same time some of them fail.

可以从应用程序的不同部分触发并行请求.例如，启动应用程序时，会将当前位置发送到服务器，并下载事件列表.

Parallel requests can be triggered from different parts of the app. For example when the app is launched the current location is sent to the server and a list of events is downloaded.

确保第一个仍在运行时没有第二个刷新令牌请求的最佳方法是什么?

What would be the best way to make sure that no second refresh token request is made while the first is still running?

推荐答案

查找令牌寿命并设置缓冲区，例如1-2分钟和如果令牌需要刷新，请在令牌刷新时保存所有请求.之后，执行所有保存的所有请求.您可以使用DispatchQueue和DispatchWorkItem来做到这一点.

Find your token lifetime and set buffer e.g 1-2 min and If your token needs refresh, save all requests when token is refreshing. After that execute all saved all requests. You can do this with DispatchQueue and DispatchWorkItem.

下面的示例代码.

final class Network: NSObject {

    static let shared = Network()

    private enum Constants {
        static let tokenRefreshDiffrenceMinute = 1
        static let tokenExpireDateKey = "tokenExpireDate"
    }

    private(set) var tokenExpireDate: Date! {
        didSet {
            UserDefaults.standard.set(tokenExpireDate, forKey: Constants.tokenExpireDateKey)
        }
    }

    public override init() {
        super.init()

        if let date = UserDefaults.standard.object(forKey: Constants.tokenExpireDateKey) as? Date {
            tokenExpireDate = date
            print("Token found!")
        }
        else {
            print("Token not found!")
            isTokenRefreshing = true
            getToken {
                self.isTokenRefreshing = false
                self.executeAllSavedRequests()
            }
        }
    }


    private var isTokenRefreshing = false
    private var savedRequests: [DispatchWorkItem] = []

    func request(url: String, params: [String: Any], result: @escaping (String?, Error?) -> Void) {

        // isTokenRefreshing save all requests
        if isTokenRefreshing {

            saveRequest {
                self.request(url: url, params: params, result: result)
            }

            return
        }

        // if token expire
        if getMinutesFrom2Dates(Date(), tokenExpireDate) < Constants.tokenRefreshDiffrenceMinute {

            // open this flag for we need wait refresh token
            isTokenRefreshing = true

            // save current request too
            saveRequest {
                self.request(url: url, params: params, result: result)
            }


            // get token
            self.getToken { [unowned self] in
                self.isTokenRefreshing = false
                self.executeAllSavedRequests()
            }
        } else {
            //Alamofire.request ...

            DispatchQueue.global().asyncAfter(deadline: .now() + 2) {
                DispatchQueue.main.async(execute: {
                    result(url, nil)
                })
            }
        }
    }

    private func saveRequest(_ block: @escaping () -> Void) {
        // Save request to DispatchWorkItem array
        savedRequests.append( DispatchWorkItem {
            block()
        })
    }

    private func executeAllSavedRequests() {
        savedRequests.forEach({ DispatchQueue.global().async(execute: $0) })
        savedRequests.removeAll()
    }

    private func getToken(completion: @escaping () -> Void) {
        print("Token needs a be refresh")
        // Goto server and update token
        DispatchQueue.global().asyncAfter(deadline: .now() + 1) { [unowned self] in
            DispatchQueue.main.async(execute: { [unowned self] in
                self.tokenExpireDate = Date().addingTimeInterval(120)
                print("Token refreshed!")
                completion()
            })
        }
    }

    private func getMinutesFrom2Dates(_ date1: Date, _ date2: Date) -> Int {
        return Calendar.current.dateComponents([.minute], from: date1, to: date2).minute!
    }
}

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